Maternal smoking during pregnancy is associated with wheeze and asthma in preschool children, even among children who were not exposed to maternal smoking late in pregnancy or after birth, according to a new study. "Epidemiological evidence suggests that exposure to maternal smoking during fetal andearly life increases the risk of childhood wheezing and asthma, but earlier studies were not able to differentiate the effects of prenatal and postnatal exposure," said lead author Åsa Neuman. MD, of the Institute of Environmental Medicine at the Karolinska Institutet in Stockholm, Sweden. "Our study, a large pooled analysis of eight birth cohorts with data on more than 21,000 children, included 735 children who were exposed to maternal smoking only during pregnancy."